Telephone subscriber



March 16, 1954 Filed Sept. 16 1949 K. s. DUNLAP ETAL 2,672, 3

TELEPHONE SUBSCRIBER 5 Sheets-Sheet l ATTORNEY March 16, 1954 K. s.DUNLAP ETAL 23 TELEPHONE SUBSCRIBER Filed Sept. is, 1949 5 Sheets-Sheet2 FIG. 2

Has v' K. s. DUNLAP 'NVENTORS W.A. MAL THANER A TTORNE V K. S. DUNLAP,ET AL TELEPHONE SUBSCRIBER March 16, 1954 Filed Sept. 16, 1949 5Sheets-Sheet 3 I l7 l8 I73 I74 I75 7 l l /4 FIG. 5

FIG. 7

IN l/E N TOPS DUNLAP 14. A MALT/MNER AT ORNEY March 16, 1954 K. s.DUNLAP ETAL TELEPHONE SUBSCRIBER 5 Sheets-Sheet 4 Filed Sept. 16 1949Ks. DUNLAP 'NVENTORS WAMALTHANER ATTORNEY March 16, 1954 K. s. DUNLAPETAL 2,672,523

TELEPHONE SUBSCRIBER Filed Sept. 16, 1949 5 Sheets-Sheet 5 V .r/M U K.DU/VLAP W. A. M41. TMNER ATTORNEV JENT/NG THE DIG/T2 AS THE EXC/ TA TIONM hmfiwvu V W .W w d A 56 m 1 l W mu 5 D3 5D m m A A n C W B H a aMkofiwA mm. W A u m u s H I M P E m E m 5 m m s M m m p r M o as n r A TA n 9 8.W E w T T S A s a. A m m mu 4 m V A A E n. 4 m V m S 3 M H a M MMQYRWJO amfiioe .35: mt Elma. 3&2 m5 mwimw ESE mt Eimmxukti at A r B n Cn m P on 2 m 2 u w. E H v n L T F F a a m M a am 6 M 6 m a M F l N l INI I N an F o F M F o F 4 F um mm m nm s a... M .3 m mm mm Wm M 3 a m AT fv E m REPRE APPLIED TO THE ONE CYCLE 0F CURFE N T flashes the centralofiice equipment by operating his switchhook or cradle contacts.

Another feature of the invention relates to supervisory and switchinequipment located at the subscribers station for associating the callingequipment at the subscribers station with the line extending through thecentral ofllce and disassociating the communication equipment from theline extending to the central oflice in response to the initiation ofeach call by the subscriber.

Another feature of this invention relates to a two-step switchingdevicein which the first step is controlled by a subscriber initiatingthe call and the second step is initiated or controlled from the centralofiice. Both steps occur simultaneously when the subscriber answers thecall.

Another feature of this invention relates to the use of a magneticholding or locking device which is positioned by placing the telephonetransmitting and receiving equipment on the cradle or the receiver onthe switchhook and then is maintained in this position when the handsetor receiver is removed from the supporting member until reversed currentis applied to the line from the central oflice.

The supervisory equipment in accordance with the exemplary embodiment ofthis invention comprises two sets of switching contacts and a magneticholding device. One set of contacts is controlled exclusively by theposition of the handset or receiver and the other set is jointlycontrolled by the position of the handset or receiver and by the centralofiice. The first set of contacts operate in substantially the samemanner as the usual so-called switchhook or cradle contacts, while thesecond set of contacts are jointly controlled by the switchhook orcradle of the subscribers set and by a magnetic holding devicecontrolled from the central office. 4 I Placing the receiver on the hookor the handset on the cradle will restore both sets of contacts to theirnormal or idle condition. The first set of contacts are moved to theiroff-normal position in response to the initiation of a call by thesubscriber removing the handset or receiver from its supporting member.The second set of contacts, however, are maintained in their normal oridle condition at this time by the magnetic holding or locking device.Later, after all signals necessary to select the called subscribers linehave been transmitted to the I final switching center employed inestablishing the call, the magnetic holding device is actuated ,or movedto its opposite position, whereupon the second set of contacts move totheir off-normal position, disassociate the calling equipment fromgthe'subscribers line and associate telephone transmitting and receivingequipment with the line, thus conditioning the subscribers stationsetfor telephone communication.

The foregoing and other objects and features of this invention may bemore readily understood from the following detailed description of anexemplary embodiment thereof when read with reference to the attacheddrawings in which:

Fig. l shows a detailed circuit of the various devices and the manner inwhich they are connected one with another at the subscriber's station;

Fig. 2 shows a top view of the subscribersstation equipment embodyingthe present invention;

Fig. 3 shows a front elevation of the subscriber's station equipment inaccordance with the exemplary embodiment set forth herein in detail;

Fig. 4 is a partial section through said equipment at the positionindicated by the section line 44, Fig. 3;

Fig. 5 shows the manual selecting devices employed in the subscribersstation;

Fig. 6 shows a partial section view along the broken line 6-6, Fig. 5;

Fig. '7 shows the right-hand end view of the finger operated settingdevice shown in Fig. 5;

Fig. 8 shows a bottom view of the subscriber's station equipment shownin Fig. 2;

Fig. 9 shows a partially broken away view of the subscribers stationequipment, along the broken line 9-9 of Fig. 3;

Fig. 10 shows a right-hand elevation of the equipment shown in Fig. 8along the section line I0I0;

Fig. 11 shows the supervisory and switching control equipment which ismanually operated but released under control of the omce equipment; and

Figs. 12, 12A, 12B, 12C, 12D, and 12E illustrate typical wave forms ofthe applied alternating current or fluxes produced thereby and typicalwave forms of pulses generated by the equipment made in accordance withthis in vention and located at the subscribers station.

Fig. 1 shows the over-all schematic of the subscribers stationequipment. As shown in Fig. l, the subscribers station equipmentincludes a handset 2I, which when resting upon the support or cradledepresses the pins 22 ,and causes the bell cranks I9 to actuate contacts24 to the right and contacts 23 to the left, as shown in Fig. 1.Contacts 24 are controlled solely by the position of the handset 2|while the contacts 23 are controlled jointly by the handset through thepin 22 and bell crank I9 and also a magnetic looking or holding device41 whichincludes the windings 21, 20. In addition, the usual inductioncoil having windings 32 and 33 is provided for transmission of the voicecurrents.

A group of saturable magnetic impulse coils 40 and 50 to 59 are providedfor generating a start pulse and ten stop pulses to represent eachpossible identity or character of each of the digits of the calledsubscribers number. The secondary windings of these coils are connectedto a manually controlled switching or dialing arrangement I30 whichpermits the, subscriber to select the designation or number of thecalled subscribers station. The manual switching or selector device I30is, in turn, connected to a plurality of electromagnetic reed-typerelays IOI through II4 of the type disclosed in United States Patents2,245,391 granted to Dickten, Jr., June 10, 1941 and 2,264,622 grantedto Ellwood, November 25, 1941. These relays are arranged to successivelyclose their contacts; and thus provide a distributor arrangement fortransmitting the pulses representing the identity of the various digitsof the called subscribers number in succession. A group of rectifiers orunilateral conducting devices, I50 through I63 inclusive, and I throughI93'inclusive, are provided to control the relays IOI through Illfof thedistributor as will be described hereinafter.

Although any suitable source of alternating current may be employed toactuate the equipment at the subscribers station, in the specificembodiment described herein the alternating- -current power foractuating the subscribers staover the subscribers line 13-18: from a.sourceat a remote point which remotepoint is usually the central=office.

In addition, phase-splitting networks comprising inductances 4|, 42 andcondenser 43 are provided for applying alternating currents inquadrature to the two sets of primary windings of the impulse generatingcoils 40 and 5.0. through 59 inclusive. An isolating and phasing networkcomprising inductance .35 and condenser 31 is provided to isolate thecircuits of the distributor comprising relays I01 to H4 and the impulsegenerating coils 40 and 50 through 59 inclusive. This network suppressestransientsdue .to the. operation of the distributor relays till, throughH4 and thus prevents these transients from interfering with theioperation of the impulse coils M3 and 5.0. through 59 or with theoperation oftheireceiving equipmentat the central office. In addition,this network is employed to properly phase the controlling currentssupplied to the distributor relays 1 through H4 .and the impulse coilsin and 50 through 59.

In the exemplary embodiment shown, provision ismade for the generationof pulses representing eight different digital positions or charactersrepresenting the called su'bscribers station during each complete cycleof operation of the calling apparatus, and these pulses are repeatedlygen erated as long as the excitation current is applied. In addition, inthe specific embodiment set forth herein pulses representing fouradditional digits are transmitted during each cycle of operation of thecalling apparatus, which additional pulses may beemployed to identifythe calling station for charging purposes or for other reasons. Whenthese extra digits are not required they will be omitted. Pulsesrepresenting any arbitrarily chosen number of digital positions orcharacters (within reasonable limits) may be generated by properlydesigned signaling apparatus. Eight digital positions or characters havebeen selected for this disclosure for representing the calledsubscribers station since eight character calling numbers are in commonuse in telephone systems. It will be understood that these charactersmay be. digits or letters or a combination of the two as commonly usedin designating telephone calls. Each of the digits 0 to 9 will berepresented, by adifferent combination of two pulses; the pulsecombination representing the digit 2 will also represent the letters A,B and .C; the pulse combination representing the digit 3 will alsorepresent the letters D, E and F; and so on. Hereinafter, eachcombination of eight characters will be referred to as each callednumber irrespective of whether the combination comprises digits orletters and digits.

In accordance with an exemplary embodiment.

of this invention, each of the pulses generated is of about 1millisecond in duration. When pulses of this duration are transmittedover various types of voice frequency communication paths encountered intelephone systems, about 3 milliseconds are required for the longesttransients to die out sufiiciently so that the succeeding pulse may beaccurately recognized without interference from the transientca-used bythe previous pulse. In other words, each transmitted pulse ofapproximately 1-millisecond duration is in effect lengthened to .a.decaying alternating current of approximately 3-milliseeonds duration.At the end of this 3-mil1isecond period or any time there.- atterasecondkpulse maybe transmitted.

The signaling system employed in this embodiment of the-inventioncomprises a start pulse of: l-millisecond duration for each character,the

start pulses being generated at about ll-millisecond intervals as longas the pulsing transformers areenergized, and a stop pulse of l-millisecond duration for each character, each stop pulse reaching its peakvalue during the 3;5 .to NM-millisecond interval of time after the startpulse has reached its peak value. In order to provide sufficient"margins of safety to permit reliable signaling, over 3.5 millisecondsare allowed for decay of each pulse and the. times of the start oitransmission assigned to stop pulses representing digits of successivemagnitudes differ by .444- milliseconds. Thus, digit 1 is represented bya start pulse followed by a stop pulse which reaches its peak valueabout 3.5 milliseconds after the start pulse reaches its peak value,digit 2 is repre--' sented by a start pulse followed by a stop pulsewhich reaches its peak value about 3.80 milliseconds after the star-tpulse reaches its peak value, and so on. It will be observed that thestop pulse for the digit 0 reaches its peak value 7.44 millisecondsafter its start pulse and 3.5 milliseconds before the next succeedingstart pulse. Thus, there is required an increment of time of 3.5milliseconds for the decay of the start pulse, 9 increments of time of.444 millisecond each for the generation of a pulse at any one of theten times necessary to represent the various digits, and a lastincrement of time of 3.5 milliseconds, all of the latter being requiredto permit a stop pulse to decay only if it should occur at the end ofthe ninth increment of time. Consequently, about 11 milliseconds of timeelapse between the start pulses of succeeding digits, from which itfollows that 11 milliseconds is required in this exemplary system totransmit each digit or character designating the called number.

In order to indicate the starting. Point of the transmission of a callednumber, a time interval of approximately 22 milliseconds durin which nopulses are transmitted is provided at the beginning of, orbetween groupsof, pulses representing a called number. Thus, a time interval of 111milliseconds is required to transmit each eightdigit called number andthe corresponding nosignal or blank period. When the subset is. arrangedto transmit extra digits to identify the calling or called station thetime of the cycle of the calling apparatus is correspondingly extended.

In accordance with this exemplary embodiment of the invention thesignaling pulses are generated by saturation-type pulse genera-tingtransformers. There are eleven pulsing transformers it) and through 59,one for each of the numerals 0 to 9 and one for the start or referencepulse. The excitation current for the apparatus may be obtained locallyat the subscribers station or, as in the exemplary embodiment set forthherein, the excitation current for-the; pulse coils is transmitted fromthe central ofice over the line which interconnects the signalingstation with the central office. This current is an alternating currentof substantially sinusoidal wave form, and at the signaling station thecurrent is, passed through a phase shifting network so. that the currentis converted to a two-phase source in 75, primary windings of thetransformers 49' and 50* through 59 are respectively seriallyinterconnected and connected with the two phases of the excitationcurrent so that one phase of the excitation current is applied to Oneprimary winding of each transformer and so that the other phase of theexcitation current is applied to the other primary winding of eachtransformer. The secondary windings of the transformers 49 and 59through 59 are connected across the line through a selector switch I39and a distributor. The magnetic core of each transformer 49 and 59through 59 is designed to be saturated except for very small values ofampere-turns, and an electric pulse is generated in th secondary windingof each transformer when the flux is changed from saturation at onepolarity to saturation at the other polarity. The flux generated in thecore of each transformer 49 and 59 through59 depends upon the number ofturns in the two primary windings of the transformer and upon thecurrent flowing in each winding. In this embodiment of the invention thmaximum value of the currents in the circuits associated with each phaseare equal. Thus, the flux generated in the core of each transformer 49and 59 through 59 depends upon the number of turn in the primarywindings of the transformer and upon the time-phase relationship betweenthe currents flowing in the primary windings. The pulse attains amaximum value when the flux becomes zero.

For this signaling system it is necessary that all pulses besubstantially alike as to wave form and amplitude and that eachcombination of two pulses representing a digit be of the same polarity.The area under a voltage-time curve representing the pulse isproportional to the total change in flux and to the number of turns inthe secondary winding. High intensity energization will produce a high,short pulse, while lower energization will produce a wider pulse havingthe same area. Thus, if all pulses are to be alike the total maximumampere-turns on each. core must be equal. Assuming equal maxima in thecurrents of the two phases and a 90-degree phase displacement, then forpulses of equal amplitude and shape the turns NA and NB of the twoprimary windings of each of the transformers 49 and 59 through 59 mustbe such that JNA3+NB =JNA +NB where NA1, Ne etc., are the number ofturns in the primary winding of the transformers 49 and 59 through 59which is connected to phase A of the excitation current and N3 N13 etc.,are the number of turns in the other primary winding of the sametransformers which is connected to phase B of the excitation current. Ifthese conditions are met and if the cores and secondary windings of allthe transformers 49 and 59 through 59 are alike the pulses will besuitable for signaling purposes.

In order to cause each transformer 49 and 59 through 59 to generat apulse at a suitable time during each half cycle of the excitationcurrent, the total ampere-turns driving flux through the transformercores must be controlled so that the flux in each transformer is zero atthe time assigned to the pulse which that transformer serves togenerate. This means that NAIA-NBIB= must be satisfied at the time thepulse is a maximum, where NA and NB are as defined above and IA and Isare the currents through NA and N8,

= a constant and substitution gives NAIO sin wtNBIo 00s wt=0 =tan atwhere IA, In, NA and Na are as defined above, I0

is th maximum current supplied by each phase of the excitation current,0: equals the frequency. in cycles per second multiplied by 21r, and tis the time in seconds.

Thus, when the angular position of the desired pulse is fixed inrelation to each half cycle of the excitation current, the number ofturns and the polarity of the winding are given by these'equa tions.

Since the magnetic flux in each transformer 49 and 59 through 59 isreduced to zero two times during each cycle of the excitation current itfollows that a combination of two pulses representing a digit must occurduring each half cycleof the excitation current and that eachcombination of two pulses representing a digit are of opposite polarityto the preceding two pulses;

Pulsing transformers 40 and 59 through 59 inclusive are interconnectedso that the A windings of the transformers are connected in series :2and connected to the excitation current through serve to apply analternating current to the A windings of the transformers which isdisplaced degrees in time-phase relationship from the alternatingcurrent applied to the B windings. Transformers 49 and 59' of thetransformers. through 59 inclusive contain two primary windings andthese transformers serve to generate the stop or digit pulses. a

As discussed hereinbefore, each of the trans formers 49 and 59 through59 inclusive is designed so that its core is saturated except for verysmall values of flux. Thus, a short pulse is generated in the secondarywinding of each transformerwhen the flux in the core of that transformerpasses through zero magnitude' These pulses are illustrated in Fig. 12which shows the various pulse positions as a function of time. Fig. 12Aindicates the ampere-turns applied to the core of transformer 49 as afunction of time and shows the time-phase relationship between the startpulses and the ampere each transformer will equal the summation of theampere-turns generated by each phase wind-' ing. As discussedhereinbefcre, since the maximum value of the current in each phase isequal and since the time-phase relationship between the two alternatingcurrents is fixed, the time at which the summation of the ampere-tumsand consequently the flux in each transformer passes through zeromagnitude is governed by the number of turns in eachphase winding. Fig.123

If each phase of the excitation.-

The phase sh ftin networks are of conventional design andindicates. therampereetmns. generated each phasexwindingof transformer Elias. afunction of time and shows thetime-phase relationship between. the stop.pulses: representing the digit 1 :and the ampere-turns generated. ineach phase winding. Figs. 1 2C and 12Dv "indicate. the timephaserelationships for the generation of stop pulsesarepresentingthe digits 2and 0, respectively. In each case the stop or digit pulsevoltage isinduced in the output winding when the summation of the ampere-turns inboth input windings equals zero, in each case two pulses: i. e. a startpulse and a. stop pulse are induced during each complete hal-fcycle-ofthe applied-alternating current and in each case each successive pulseis of opposite-polarity tothepreceding pulse as induced by the sametransformer. It will be apparent that the particular phase relationshipsindicated are arbitrary-and that other relationships would serve equallywell.

As shown in Fig. 1-, each pulsing transformer is connected to lines 13and M through condenser 12. This condenseris proportioned to theiterative impedance of the line and to the impedances of the secondarywindings of coils i and "50 through 59-, inclusive, so thateachhalfcycle pulse as generated by a transformer is applied throughcondenser T2 to the lineas a complete cycle of alternatingcurrent ofsinusoidal wave form; and the period-ofeach complete cycle ofalternating current is equal tothe time required for eachhalf-cyclepulse as generated by the transformers.

Fig; 12E indicates the start pulses and pulses representing thedigit. 2as applied to. the line during one cycle of the excitation, current.Fig. 12E in conjunction with Figs. 12A and 12C indicates therelationship between the pulses. as generated' in the transformers andthe pulses as applied to. the line.

An excitation current which alternates. at 45 cycles per second is.employed for this embodiment of the invention. However, it will beapparent that other frequencies would serve equally well.

The primary windings, of each of the trans I formers 50 through 59',inclusive, are. proportioned so that each transformer generates a stop.pulse corresponding to the digit. assignedto that transformer. Thus,each. of these. transformers generates a pulse which reaches its peakvalue at. atime during, the i -millisecond interval. assigned to stop.or digit. pulses and there isa miilisecond time interval between. the.peak. values at each. pulse generated.

. During. the time. that the excitation. current. is applied to the.pulsingtransiormers apulse isgencrated, inthc secondary. of eachoithetransformers during each half cycle. of the excitation cur rent. Inorder to. apply therpulsestotheline comprising. conductors l3. and 1.4.in, conformity with the called number which. it. is. desired totransmit,

selector switch I and the distributor are employed to interconnect the.transformers with the line.

A selector: switch serves to interconnect. the: pulsing transformers.with the line. through. the distributor; Thus, pulses representing anyof the digits 0 to 9: may be impressed across the telephone line inaccordance with the'setting of the selector switch.

selactondials H to: la andrelease lever [33 are accessible to anoperator. The selector dials are made of a non-conducting material suchas hard rubber or plastic, and each dial is provided with r is providedwith ten grooves which correspond to the finger indentations on theouter periphery of the dial. Thegrooves-on eachdial serve to wage with adetent pawl 36 to secure each dial in one of the ten possible positionsas selected by the operator. As indicated in Fig. 6, detent pawl 36which cooperates with dial. I5.- is pivoted. about shaft 143-6. Spring46' is attached between support Hit-and pawl 36 so thatpawl 3 6 isnormally-forced against dial l5, thereby securing the dial in a fixedposition by engaging with one of the ten grooves. Spring as also servesto apply a continuous force to support I66 which tends to rotate supportI66 and dial it in a clockwise direction about. shaft 29. The grooves onthe dials and the; detent pawls are shaped andpositioned sothat bypressing upon, the finger indentations in a. dial an operator can movethe dial ineithendirection and so that the ratchet action of the pawlagainst the grooves secures. the dial in any one of the: ten positionsto which it may be moved. The; rotary movement of the dials is limitedtoabout onefourth oi a. revolution by stop: I 3land insulator l9=l..

Release arm [38 is connected with release lever I3-3 through lever [34-and is provided. with slots to. engage each detent pawl. When leverI33is in its normal position, arm I38 permitsweach deitent pawl toengage with a groove in the corresponding dial. When. lever 133isdepressed, arm I38 is, moved in: a clockwise direction about shaftI35. and the detent pawls are disengaged from the dials, therebypermitting the spring associated with each-dial to causeeach dialto'return to its initial position- Aspring contact; is connected to eachdial, and each. dial. and. spring contact may be moved so that thespring. contacts may be connected with any one of ten conductors. Asindicated in- Fig. 6., spring contact 26 isattached to dial Hi and.itxis' electrically connected toterminal 146 through conductor 56.Insulator till supports-the various terminalsand conductors, andthe tenconductors Bl to 10 which. may be. contacted: by springwcontacts mountedthereon.

The. distributor arrangement. comprises fourteen relays, Nil to N4, of.the; type disclosed in. the above identified patents: to Ellwood and;Dick tenand each of the relays. in the specific embodimentset forthherein comprises an individual coil surrounding. two normally open reedrelay con-- tactsv I 29 and 12!. These reeds aremade'of magneticmaterial and sealed in a container which may be of glass or othersuitablematerial. The. reeds are. polarized by means of oneorm0re;.permanent magnetsv so.- that reeds normally'remain,

' open. However, when a current of one. polarity within the operatingrange flows. inthe. winding the. contacts will not close but when. a.currentoi. the same or smaller, magnitude. of the. opposite. polarityflows through the winding surrounding,

* these contactsthe' contacts will close. When the until the currentagain flows through the wind- :ing in the operating direction. Inaddition, a

common winding 38 is provided for all of the relays and surrounds all ofthe reeds and their associated polarizing magnets in such a manner 'thatwhen a current of sufflcient magnitude is passed through the winding thereeds oi? a predetermined one of the relays will be actuated in theopposite manner to that which the reeds of all the other relays areactuated. This behavior may be accomplished by reversing the sense ofpolarity of the polarizing magnet and of the operating winding of theone relay from the sense of the polarity of the polarizing magnet andoperating winding of all the other relays.

It is to be noted that the right-hand reed I2I in each of the relays isemployed to interconnect successive ones of the digit selectors IIthrough I8 of the selector switch I39 with the common conductor 39,whereas the left-hand reeds I2ii are employed to control the operationof the relays of the distributor.

Assume now that the relays IIlI through I I4 are positioned with thereed contacts in relay I99 closed, while the reed contacts of all theother relays are open. Further assume that controlling frequency forcontrolling the reeds is applied between conductors 48 and 49. If thealternating current between the conductors 4B and 49 is in such adirection that the upper conductor 48 is negative with respect to 49 atthe time the contacts of the relay I09 are closed then a path iscompleted by the closure of the left-hand contacts of the relay I I59from conductor 48 through the left-hand contacts of relay I09, rectifierI81,

winding of relay I 98 to conductor 49. Current flows in the above pathin such a direction as to maintain the reed contacts of relay I98 open.This is indicated diagrammatically by the arrow shown within the relayI08 which indicates the direction which the current must flow betweenthe windings of this relay to cause its contact to close. When thecurrent flows. in the opposite direction the relay will open thecontacts as described above. When the alternating current changespolarity so that the upper conductor 48 becomes positive and the lowerconductor 49 negative then current ceases to flow through the winding ofrelay I08 and flows from the upper conductor 48 through the left-handreed of relay I09 and through the rectifier I88 at this time and throughthe winding of relay I II] in such a direction as to close its contacts.Upon closure of the left-hand contacts of relay I I0, current also flowsfrom the upper conductor 48 through the lefthand contacts of relay IIIlthrough rectifier I58 and the winding of relay I 99 to the lowerconductor 49. This current flows in such a direction as to open contactsof the relay I09 and interrupt the current flowing through the windingof relay III). The contacts of relay IIII however remain closed at thistime so that current continues to flow through the winding of relay I99in such a direction as to maintain the contacts of this relay open. Whenthe upper conductor 48 again becomes negative current flowing throughthe lefthand contacts of relay IIIl reverses and flows through thewinding of relay I I I and rectifier I59 instead of throughjthe windingvof relay I09 and rectifier I58. The direction of flow bfc rren throughthis Winding is such as to cause the reed contacts of this relay toclose and complete a circuit through the left-hand contacts of relay I II and rectifier I89 through the winding of relay H0 in the reversedirection thus causing this relay to release. In this manner thecontacts of each of the relays are closed for one-half cycle of thealternating current between conductors 49 and 49.

Furthermore, upon each reversal of the voltage between these conductors48 and 49 the reed contacts of the succeeding relays are closed and thereed contacts of the previous relays are opened. Consequently, thecontacts of reeds close in succession, each one being closed forapproximately one-half cycle of the applied controlling alternatingcurrent.

The manners in which the various devices and circuits cooperate witheach other to form a subscriber's subset capable of cooperating with aswitching system to provide improved service will now be described.

The circuits as shown in Fig. 1 are in their normal or idle condition.At this time the ringer 30 is connected in series with condenser 3Iacross the tip and ring conductors I3 and I4 extending to the centralofllcc. At the central ofilce, battery is normally connected to one ofthese conductors and ground to the other conductor thus placing a chargeupon the condenser 3 I. I If the subscriber is called, ringing currentwill be applied to these conductors at the central oiiice and cause theringer 30 to ring and call the subscriber. When a subscriber answers, hewill pick up the handset 2| and allow pins 22 to rise. As a result, thecontacts 24 will be moved to their left-hand position as shown inFig. 1. As shown in Fig. 11, the pins 22 in rising cause the bell cranksI9 to rotate in a clockwise direction. As a result, the contacts 24close and the member II is rotated in a counter-clockwise direction awayfrom the armature 25 of the magnetic lock or relay 41. The polarity ofthe voltage applied to the tip and ring conductors I3 and 14 at thecentral office is in such a direction at this time as to move thearmature 25 to the right as viewed in Fig. l and also in Fig. 11 withthe result that the contacts 23 are also switched to their opposite orright-hand position.

With both contacts 23 and 24 actuated to their operated positions, thesignaling equipment at the subscriber's station comprising the impulsecoils 40 and 50 through 59, the selector switch I30 and the distributorrelays IIlI through II4 inclusive are disconnected from line conductorsI3 and I4 and the transmission apparatus and circuits including thetransmitter and receiver of the handset 2I and windings 32 and 33 of theinduction coil and condenser 34 are connected to the tip and ringconductors I3 and I4 extending to the central office to provide theusual subscribers transmission circuit and to supply necessary batteryto the transmitter 01' the handset 2I.

The circuits then remain in this condition so long as the subscribersare talking over the established circuits. It should be noted thatthroughout this time a direct-current path exists between the conductorsI3 and 14 extending from conductor 13 through the left-hand operated setof contacts 24, the right-hand operated set of contacts 23, inductioncoil 33, the transmitter of the handset 2| and the right -hand set ofoperated contacts ofthegroup oi contacts 24 to conductor H. extending tothe central oflice. Variations inthe'transmitter resistance producedibythe voice waves arethus transmitted in the above described circuit tothe central. ofllce. In addition, they induce currents. in the.secondary winding 3-2 of the: induction coil which currents flow in acircuit which extends from the common connection between the transmitterandreceiver through the -left-hand winding 32 of the. induction coil,through. the central set of; operated. contacts of agroup of contacts23, and. through the-receiver and: back to the. common. points betweenthe receiver and transmitter.

Voice currents arriving over conductors l3 and II transmitted over theabove-described circult,..including the winding 33 of induction coil andthe transmitter .of. the handset induce currents in. the left-handwinding .32. connection to the receiver in the manner described above.The condenser 34 is connected between the upper terminal of winding 32and the transmitter and increases the transmission :emciency ofthehandset in the usual, manner.

At 1 the termination of the call, the subscriber will: replace thehandset 21 upon the cradle or supporting members and cause pins 22 to bedepressed. As a result, the group oi: contacts designated .2 will beactuated to the right as shown in Fig. 1, while the contacts 28 will beactuated to the left. In addition, thearmature 25 of the switching relayis also actuated to the :leit. At this time the direct-current pathbetween conductors l3 and. I4 is interruptcdand the ringer 30 andcondenser 3| reconnected between the tip and ring and. the. normalbattery potential applied'to the conductor at theacentral ofiice thusrestoring the charge on condenser 131' to its normal value.

When a subscriber at the substation described herein in detail desiresto. make a call, he will first ascertain. the number or designation ofthe 1" subscriber with which he wishes to communicate. The subscriberwill then set the selector switch 130 of Fig. 1,. which is also shown.in Figs. 2,, 3, 4, 5, 6, 7, 9 and .10, by placing his finger overthedesired letter or numeral for each digit in the ratchet wheels H to18 and then moving these wheels downward to the guide or stop member,which may form a part of the front of the case. of the subset asindicated at 13.9. :in Figs. 3., 4, 5, 6 and 7.

After the subscriber has moved each. one of these dials or wheels inthis manner; he may check the setting, oi therinstrumentsto be sure thatit is set in accordance with the designation of the desired subscribersstation. At thisntirne this designation. appears :in thexfirstllineabove the sto or guide member 139.

If the subscriber has made an error in setting these selector discs, hemay correct the error in. either of two ways. 1) He may adjust thesetting of the individual discs that are not set as he desires, or ('2)he :may' release them all :by' operation of button 1.32. shown in Figs.2 and .3 which depresses the lever I 33, shown in Figs. 2,. 5, and "I,which :leverthen 'moves the. link member I35 downward and rotatesthelatchcontrol plate 138 in :a clockwise direction and is viewed in Figs.6 and 7. The member 138 then engages the pawls .or latches 36 associatedwith each ,of the selector discs and rotates these latches in aclockwise direction, thus disengaging theseupawls or latches fromv thenotches on the inside. oi-thc discs 'aswshown. in 5 and per .m-its thesediscs to. be "restored; to their original or.' ,zero;position1.-afterwhich: the subscriber may 14 again set, them in accordance. with thedesignation. of the desired subscriber's station.

After the subscriber has set these discs and checked the accuracy of thesetting, he is ready to place small. It should be noted that in settingeach disc, a brush carried or supported by each: of the'discs. passesover a group of ten contact bars ill to 10 and makes contact with one ofthese bars depending upon the. position in which the disc is set by thesubscriber. Thus the brush 26 attached to each of the discs makescontact with a corresponding one of the contact bars when the subscriberhas set the disc. in accordance with the desired number- Such con.- tactarrangement is represented graphically by the selector member I inFig. 1. wherein the brushes attached to the discs are designated 1.!through l8. These brushes are moved in engagementwith the horizontalbars or conductors as shown in Fig. 1 and represented by the bars 61through "Hl in Figs. 6 and 7.

After having set these discs, the subscriber. will then pick up thehandset 21 which will allow the pins 22- to rise. The bell crank 18 thenrotates and permits bothv groups of contacts. 23 and 2.4 to be actuatedto their operated position. Contacts 24 do so move and are actuated totheir left-hand posit-ion as shown in Fig. 1. However, the armature 25-of the relay or magnetic holding-device d1 maintains the. set ofcontacts 23 in their normal or operated position at this time due toresidual magnetic attraction between the armature and left-handpole-piecewas shown in Fig. l.

The contacts 24 in being operated totheir lefthand position connect thecondenser 31 across the terminals of the common winding 38. surroundingall of the reeds of the reed relays llll through H4. The condenser 3ldischarges in this circuit and in discharging closes the reed contactsof one of the relays and opens the reed contacts of all of the otherrelays which may be closed. Assume, for example, the contacts of I I0are closed and the contacts of all of the other relays are opened.

As described hereinabove, the permanent magnet associated with the reedsof relay H0 will then maintain these contacts closed until opened by thereversed magnetic field due to a reverse current flowing through itswinding.

Contacts 24 in moving to their left-hand position also connect conductor.13 through the lefthandoperated contacts 24 and right-hand normalcontacts 23 to the upper terminal of winding 21, and connect conductor74 through the right-hand operated contacts 24 and the left hand normal.set of contacts 21%- to the lower winding terminal of winding .28. Theother terminals of windings 21 and 28- are connected together and to thenetwork comprising inductor 35 and condenser 3-1, Thus, the windings ofrelay 2-! provide a direct-current path between conductors 13' and 7-4at this time and provide a. path from each of these conductors to thenetwork comprising the elements and 3?.

At. this time, a circuit also extends from conductor .14 through theright-hand operated contacts .24 and the left-hand normal contacts 23'to the. left-hand terminal .of the secondary winding of'the impulsecoil 40. This circuit maybe also. traced through this winding of coil 40to the commonconductor 15 extending toe. terminal of a secondary windingof reach oithe saturable puls'eicoiiswifl through. .58.. 'Ifhe'circuitwill later then through various ones of :thesexcoil's and the selectorswitch I30 to the right-hand set of reed contacts of the respectiverelays iI through I08 or to the corresponding contacts of relays I09through I I2, independent of the selector switch I30. The circuits thenextend from the contacts of relays IOI through II2 to com mon conductor39 and then through condenser I2, the right-hand break contacts ofcontacts 23, the left-hand operated contacts 24 to conductor I3extending to the central office.

The connection of the windings 21 and 28 between conductors I3 and I4extending to the central office, as described above, causes current toflow from a central oflice over these conductors through a relay orother responsive device in the central office and also through thewindings 21 and 28. The polarity of current flowing through thesewindings at this time is such that it maintains armature 25 in itsleft-hand position as shown in Fig. 1.

The equipment at the central ofiice responds to the current flowing overconductors I3 and I4 and through the windings 21 and 28 and causes theline at the central oflice to be connected to a receiving andregistering circuit. Upon connection of the line to this circuit at thecentral ofllce, the central oflice equipment will be con-- ditioned torespond to the calling signals transmitted from the subscribers station.In addition, the equipment at the central office interrupts the supplyof direct current to the conductors I3 and I4 and applies alternatingcurrent between both of these conductors and ground. The armature ofrelay 25, however, still remains in the position shown due to theresidual magnetic induction of the permanent magnets employed in thisdevice. The alternating current applied to both conductors I3 and I4 atthe central oflice flows over these conductors and through the twowindings 21 and 28 in opposition so that it does not produce anyappreciable magnetic eii'ect upon the magnetic locking device 41. Thealternating current then flows to the network comprising elements 35, 36and 31. This network is provided to suppress switching transients whichmay arise due to the operation of the distributor relays and thusprevents these transients from adversely affecting the operation of thepulse coils 40, and 50 through 59. The suppression of these transientsalso prevents said transients from interfering with the operation of theequipment at the central exchange. This network also controls themagnitude and phase of the alternating voltage between conductors 48 and49 so that a voltage sufficient to operate the relays at the requiredtime and speed is provided across these conductors, which voltage has aphase such that the distributor relays advance on each half cycle beforethe pulses from coil 40 are generated during each half cycle. Thiscurrent consequently flows from the conductor 49 through the winding ofrelay I09, rectifier or unilateral conducting device I58 and left-handreed contacts of relay III) to conductor 48, assuming that the firsthalf cycle of the alternating current applied to conductors I3 and I4 isof the negative polarity. From conductor 48, the alternating currentflows through the phase shift networks comprising inductors 4I and 42and condenser 43 and then through the two sets of primary windings ofthe saturable impulse coils 40 and 50 through 59, inclusive. Thereafterthe alternating currents flow through the resistors- 44 and 45 toground. As described hereinbefore; the two phase shifting networks 4|and 42 and condenser 43 cause the alternating currents flowing throughthe two primary windings of the impulse coils to be displacedsubstantially 90 degrees in phase. As described above, during each halfcycle of this alternating current, a pulse is generated in output orsecondary windings or each of these impulse coils. These pulses aregenerated at different times in the manner described above. The pulsesare first generated in the secondary or output windings of the startcoil and thereafter in the output windings of each of the successivesaturable magnetic coils through 59, inclusive. Such a pulse isgenerated by each of the coils for each halt cycle of the appliedalternating current. Thus, if the first .half cycle is substantiallycomplete, such a pulse is generated by each of these coils. However, inthe usual case, the phase or this pulse and frequently the pulsesgenerated for the next two or three half cycles will not be accurate sothat these pulses usually are not employed at the central office becausethe circuits of the central oiiice will not have had time to becomeproperly conditioned to receiving these pulses. Furthermore there may besome transient currents which will interfere with the proper generationof these pulses at this time so that these first pulses are generallyignored. However, when the alternating current reverses, after the firsthalf cycle whichyas assumed above is negative, or if the first halfcycle applied to the specific subset described herein in detail ispositive then current flows from the conductors I3 and I4 and throughthe windings 21 and 28 in opposition to conductor 49 and then throughthe winding of relay III, rectifier I59, left-hand operated reedcontacts of relay IIO to conductor '48, and then through the impulsecoils and phase shift 'networks to ground as described above. Thedirection of flow of current through the winding of relay III at thistime causes its reed contacts to close and in closing, the left-handreed contacts complete a circuit from conductor 49 through the windingof relay IIO, rectifier or unilateral conducting device I89 to conductor40, through the left-hand operated reed contacts oi. relay II I and thento ground in the manner described above. The direction of flow ofcurrent through the winding of relay H0 at this time is in such adirection as to cause its contacts to open. Thereafter the contacts ofthis relay remain open until the relay is again actuated. During thishalf cycle the pulses will be generated by each of the impulse coils asdescribed above.

During the'next succeeding half cycle of the alternating current, acircuit is completed from conductor 49 through the winding of relay II!and unilateral conducting device I90 to conductor 48 through theleft-hand operated reed contacts of relay I I I and then to ground asdescribed above. Current is flowing through the winding of relay H2 atthis time in such a direction as to'close its contacts. When thecontacts of relay II2 close, a circuit is completed through the windingof relay III from conductor 49 through the rectifier I and closedleft-hand contacts of relay II2 to conductor 48 and thus to ground. Thedirection of the flow of current at this time through relay III is inthe reverse direction and causes this relay to open its contacts.

During each of these half cycles, certain of the impulse coils areconnected to the transmission circuit as willbe describedhereinafter.How ever, as pointed out above, the equipment at the ae'zaaaa centralofiicawill usually. be. designed .to employ these first few pulses. forconditioning theequipment to accuratelyslrespond. tothe succeedingpulses.

Under. the assumed conditions, at the beginning of thenexthalflcyclethe. contacts or. may I13 wilhclose and. causethecontacts. of relay I 'I 2 to.- open. The closureofs thel-rightL-handcontacts of relay. I iii-at this. time connectsconductors Wand? will betransmitted over lines-13. and 14 even though such pulsesare..generat'ed during. this half. cycleby the various coils.4fIfiandT5lfll through 5.9., inclusive; likewise, at the. beginning. of.the nexthalf 1 cycle ofiithe alternating current,. the contactsofirelayLIA close-.ina manner similar to. the operation ofithe previous relaysand the contacts of. relay: lllfl open... During this.lhalfi cyclertheright-hand contacts. of; relay I II similarlyshortcircuit. or connect.the conductors 13f andt'll together through condenser. 1.2 andpreventthe transmission. of..- pulses to. the. central oilicev These twoha-lf. cycles. during. which no pulses oi the impulse coil 52 and thesecondary winding, of; the start pulse coil 40 and.through'thetleftihand. break contacts 2'3 and theright-hand'operatedcontacts 24 to conductor I4.

It is noted that the windings 21' and 28 ofithe polarized. relay orlocking device 41.: are" also shunted across these conductors asdescribed above. Howeventhese windings. offer high impedance to thepulses transmitted: to the central office and thus donot materiallyinterfere. with the transmission of these pulses.

A. shorttime later. during the same half cycle and in. the positionindicated in Fig. 12' for the No. 2 or C character ofithe, digit orsymbol" of the called subscribers number; a pulse isigenerat'ed in thesecondary winding of the impulse" coil 52 which pulse islikewisetransmitted over? the" conductors 13 and M to the central. ofil'ce overthe same circuits describedlabovewith reference to the start pulse.generated in. the secondary Winding of coil 40'. These twop'ulses asline to the central ofi'ic'e to have a' .wave formare-transmittedconstitute alb'lanli. interval and' explained above,identify the character of" the firstdigit or symbol of the calledsubscriber'sand condenser 12,. together with the secondary winding. ofcoil 40 for the stop pulse comprise'a pulse shaping or" filter elementwhich tends? to eliminate the highirequency.components 'ofthese pulsesand cause the pulses transmitted over the approximating. a single. cycleof a' sine .wave'.

.During the next half cyclethe' reed'corit'acts of relay I 02 will closeandcause'the contacts of relay IUI to open. Closure ofthe contacts ofrelay IIl2andth'e opening'of the contacts of relay' IIII occur very nearthe beginning of thehalt cycle. Consequently when the start'pulse isgenerated by coil14ll it. is transmitted overfa circuit" extending from.conductor theIright-ha'nd operated contacts 24, the left-hand ldre'akcon.- tacts 23,. through the secondarywindimg of coil 54', the selectordisc brush. Iz'iwhichis. assumed to be positioned inconta'ctwith- No. 4'segment as shown in Fig.1, the left-hand closed" reed cont'acts of relayIIl2' to common conductor 39 and and the contacts ofrela'y I l'liop'en.At thistime 1 '1 indicating thatthe first letter designation of thecalled subscribersstation is an A; B- or C. Assume; for'example; thatiti's' a" C. During this half cycle; the right-ehand'contactsf I21 ofrelay IOI" are closed 'andconnect thehrush arm-I"I tothe"commoncondiictbrtfli'- Consequently; when Y the" start pulse coil 40generates a pulse, this pulse istransmitted over the following path toconductors I3 and 1-4 to"the"central"oflice; This path may betracedfromconductor 13 through the left lfranrlv operatedcontaicts 24; th'eri'ghthand break contacts 23, condenser 12-, common conductor 39,right-hand contacts IZI' ofi'relay I'll'i',"brush"arm 'I I5- the-Ndg2horizontal conductor of'the 'selectorswitch I30"; the 'secbnda'rywinding then through condenser: 12 an'd'throu'ghthe righthand contactsofconta'cts'l tan'd th'left' hand-operated set of contacts of" contacts 24 to theconductor T31 extending to the central office;

A short time later the" stop" ordigit pulse is generated i'ncoilElvlhi'ch is'" likewise tra nsmittedi through the same Circuit/ toconductors I3 andltextending to the central. ofiibe? It is to: be"noted" that the pair of pulses transmitted during thetime the contactsof relay I11 I' rare" closed" has one givenpolarity while. thepairofpulses transmitted during-the itime the ccntacts of relay- I D-Z-are closedhas. the. opposite-polarity. The reversal of polarity of thesuccessive pairsot pulses is. illustrated. .inEigsa 12,. l 2A,,..12B,.-12C, 12D, and'lZE; in. which the -successive...pulses transmitted duringsuccessive .hali" cycles are. shown. to be "of opposite: polarity.

As shown in Fig; 1"" byi'the" dotted lines the selectorswitch I30 hasbeen" set to transmit a number assumed to be CHE-T0740: Consequently,during the-sedo'nd ha-if' cycle after the 'blan'k interval; pulses will"be" transmitted fromc'oils I and '54 designating G'; H or'l which wehave as sumed to be H. "D'uring' tl'iethird' lialfcycle' p'ulseswillhetransmitte'dfrom coils flfl-"and 53': during the fourth half 'cyc'lepui'ses will be: trans"- mitted by coils Mlwaficl 5 I-"'-and-will betrans-- mitted through the contacih of rel'ay I'II'K Y during each halfcycle following the blank interval a pair of pulses is transmitted undercontrol of one of the brush arms it through It, inclusive as positionedby the selector discs designa the number of the called subscriber'sConsequently, during each half cycle a :lses is transmitted designatingeach Y t e digits or symbols of the designation. ch of pulses istransmitted during the are operated. During the ninth half e thesucceeding three additional half es relays ills through H2 operate and ct four additional pairs of pulses. These transmitted to identify thecalling subme. i s ation. As shown in the drawing the 1; hand reedcontacts of these relays are connected to output windings of coils El,55,. 53 and E32. thus indicating that the last four or any other groupof digits of the calling subscriber? 'gnation comprise the number 7532.CODSBQ'L ly this information is also available to erp. Jment at thecentral oflice for switching pure as well as charging purposes if andwhen it ,sired. Thus during the ninth half cycle the pair of digitsidentifies the numeral 7 while the pair during the tenth half cycleidentifies the numeral 5, etc.

Atthe end of the twelfth half cycle and at the beginning of thethirteenth half cycle relay H3 in be operated and effectivelyshort-circuit the line conductors l3 and ill to the pulses so that nopulses will be transmitted. during this half cycle. During thefourteenth half cycle relay Me!- likewise operates and causes relay H3to Relay I M as described above also prevents transmission of any pulsesto the central These two intervals during which no .re transmittedcomprise a blank interval I ribed above to indicate that a completedesignation or calling code has been transmitted and that a succeedingone will start following th blank interval. Thereafter the above cycleoperation of the calling equipment at the scribers station is repeateduntil the circuits the central ofiice function to change the connectionsof the subscriber's station.

The equipment at the central office in respondto one or more completesets of Signals or portions thereof will establish switching paths theswitches from the calling subscribcrs line towards the calledsubscribers line. When the connection has been extended to thesubscribers line the central ofilce equip- ..t arranged to interrupt thealternating rent applied between both of the line conductors l3 and Mground and apply a di rect-c"r:ent voltage between these conductors ofsed polarity.

The details of the operation of the central oilice equipment in responseto the calling signals transmitted from the subscribers station also thedetails of the arrangement for interruptine; the application of thealternating current to the line conductors l3 and 14 at the centraloflice and the application of a directcurrent voltage of the reversepolarity between them at this time is described in detail in the aboveidentified application oi Malthaner and Vaughan which application ismade a part of this application to the same extent as if fully forth andrepeated. herein.

Interruption of the alternating current stops the operation of theimpulse coils 40 and 50 through 59 andalsdstops the operation of thedistributor relays lfllthrough H4.

The application of the direct-current voltage between conductors 13 and14 in the reverse direction causes the" armature of the magnetic relayor holding device 25 to operate to its righthand position and thuspermit contacts 23 to be operated. At this time both contacts 23 and 24are operated and thus as described above the transmitter and receiver ofthe handset 2| are connected to the windings 32 and 33 of the inductioncoil and to the line conductors I3 and 14 extending to the centralofllce. At this time the impulse coils as wellas the distributor relaysand the selector switch I30 are disconnected from th'eline so that theydo not in any way interfere withthe transmission and reception ofthevoice currents. Thereafter the circuits at the subscriber's stationremain in the position described so long as communication takespla'cebetween the subscribers and so long as the handset 2|, is removedfrom its supporting yoke or cradle and pins 22pm elevated.

Upon" the completion ofthe call the handset 2| will be placedup'on itssupports and the pins 22 depressed whereupon both sets of contacts 23and- 24 are actuated tothe positions shown inthe drawing. Likewise thearmature 25 of the magnetic holding device is moved to itsleft-handposition as'shown in the drawingwhere the circuits tothesubsciibers station are returned to thelr'normal or idle condition readyto respond to a call from the central office or to be utilized inmakinga call to another subscriber in themanner described above. I

It is to be understood that the above-described arrangementshreillustrative of an application of the principles of this invention.Numerous other arrangementsv and modifications may be devised by thoseskilled in the art without departing from the spirit and scope of theinvention.

What is claimed is:

1. A telephone subscrlbers substation apparatus comprising voice currenttransmitting and receiving equipment, call signal generating equipment,a subscriber's line extending to a central office, and switchingequipment for connecting said transmitting, receiving, and signalgenerating equipment to said line including a set of manually controlledcontacts for connecting only said signal generating equipment to. saidline, another set of contacts, a manually operable member formechanically moving said other contacts, magnetically controlled meansfor controlling the movement of said other contacts, and apparatusresponsive to signals received over said line for controlling saidmagnetically controlled means to connect onlysaid transmitting andreceiving equipmentto said line.

2. A telephone subscriber's station set comprisinga two-positionmagnetic holding device, means responsive to terminating alcallformechanically positioning said holding device in one position,-apparatus.responsive to the initiation of a call for mechanically permitting saidholding device to assume another position, means for preventing themovement of said magnetic holding device to another position, andapparatus responsiveto current of a predetermined polarity. for movingsaid magnetic holding device to another. position, l v 3. In. atelephone switching system. a subscribers station set comprising amagnetic holding relay; 9. set of contacts controlled by said carapacesubscriberra:'seconwsetpiffcontactsrjointlylrcoiw trolled'baidisubscrilieriandsald"magnetidholds ing'; relay, a lineinterconnectingsaidsubscribers. set withia switching stationymeans forinttiatingacallinfresponse'to"theiactuating'fof said con tactscontrolled,Tby*said""subscriber: otner appa ratus responsive -toriapredetermined electrical polarity' rec'eived,oversaid line foractuatingsaid holdingjrelayifor'setting saids'econd pairof'con tactsfltelephone? transmitting and receiving" equipmentinclude'd: in saidsubscriberssetfand i connections controlled by tbie-"actuatiom of 'both'of"sa'id"*'pairs" of bontacts fdr connecting said telephone"transmission" equipment to* saidyline'r- 4? 'Ina T;t1phbnG'TSWltChiIlg"system's asub scribu"s:"set;-- a" line extending r'from' said subscribrs "set .to" said "switching system: voie'e 'current "transmittihgandfreceivingtequipmentr call signal generating equipment 'comprising" ase lectorzswitch, a"p lur.ality"of impulse coils; andn relay"distributor? afi'rst"set' of "switching ficon tacts mechanicallycontrolled?asecondset of contacts jdintlyiicontrolledinneehanically atsaid subscriberisisetsandsmagneticaliy controlled from said switchingsystem; apparatus responsive to the actuationa-oftherfirst setpfr.contacts. for connecting said calling apparatus to said line, a centertapp'edtwindingdncludedrin said magnetic devicelhaving the end terminalsthereof con nected'to said line apparatus. for supplyingaltennate'currentfrom saidbiantehtah to sairl'sirne pulse coils. and'to said'rela'ys" for actuatingisaid impulse (coils; and said relays, meansresponsive tosal predetermined "signalin'g' conditionlappliedtorsaidnlineior causing said magnetic deviceto permitsaidjsecdndsetofcontactsyto be actuated. andlcirlcuits; controll'dby' tli, actnatiorr;of Isaid second; set of "contacts for 'di'sconnectiiigtisaidcallingdevic'e from said line ,andfconnectirlgsaid voicecurrent'transmitting, andi'ece'ivingapparae tus to saidline.

5. In a telephone switching system, a subscribers line, a subscribersset connected thereto comprising in combination a first set of contactsmechanically controlled at said subscriber's set, 4 a second set ofcontacts jointly controlled manually at said subscribers set andelectromagnetically over said line, a relay distributor having aplurality of electromagnetic relays included in said subscribers set,apparatus responsive to the actuation of said first set of contacts forsetting said relay distributor in a predetermined condition, and othermeans responsive to the actuation of said second set of contacts fordisabling said distributor.

6. In combination in a telephone subscribers station apparatus, voicecurrent transmitting and receiving equipment, call signal generatingequipment, a subscribers line, switching equipment for connecting eithersaid voice current transmitting and receiving equipment to said line orfor connecting said signal generating equipment to said line, saidswitching equipment including a set of manually controlled contacts,another set of contacts jointly controlled manually and magnetically,and apparatus responsive to signals received over said line fordisconnecting said signal generating equipment and" said switchingequipment from said line.

7. In a telephone switching system, a subscri'bers station set, asubscribers line terminatin thereat, a set of contacts controlled bysaid subscriber, a magnetic holding relay, a second set of contactsjointly controlled by said subsdriber and said magnetic holding relay,means for inireceiving equipment,

tiatins ar'calllinirespunse roam: actuatibniof said contacts-controlledby said subscribery -othe1-ap paratus'fresponsive ton rprede'terminedelectricalconditiontconnectedto said line lfcn actuatingsaidholding-relay*to*actuate said'second set or" contactsfl'telephonetr'ansrnitting "and-receiving equipment include'diin "said subscribersset; and

connections"controlledmy: the actuation of both of saidrsets' ofcontactsr-for -conn-ecting said *tele phone transmitting" and' receivingequipment "to said liner and disconnecting said holding relay fromsai'd'line:

' 8!" In a"'telephone switchlng" system a sub scribers station set,a.sub"scriii'ers"lineterminat ing' thereat;"a'" setfOfCOIIta'CtSI'COIItIOHfid by said subscriber; a magnetic holding relay,'a' second set of Tcontactsj ointly controlled by said' subscriber andsaid'tnagnetic holdihg relay," means for inttiating acall *inresppnse"toi'th'e" actuation-"ofsaid contacts"controlled by said'subscriber,otherap paratusresponsive tofa predetermined electrical polarityconnected*tchsaid line'for actuating said holdinggrelay'toactuate"said'second set or contactsi andlconnecti'ons 'controlled"by"the ,actua' tioiriof rs'aid'fsecond *set' ofi'fcontacts for discon=necting said h'olding relay frbmsaid liii'e.

92111.1? atelephhne "switching system, i 21' sub scribersstationsetcomprising,imcombination a subscribers Ii'nesa firstsetof contacts"manually controlled hymns subscriber, a -second set :of contacts'jointly'controlledbysai'd subscriber and bythe;'electricahcondition"offsaid "line, a source of signaling energy;and connections for applying a predetermined polarity *conditidrrtosaidline for operatiiigboth sets'of contactsinresponse to the answeririg ofa c'all'atsai'd subscribers' station.

10. In a telephone.switchingsystem, a,.sub'' scribers line, asubscribersstation'set connected th'eretd' comprisinggai firstfset'otcontacts con,nected lt'o said ,lihe mechanically ,jcontrolle'd ?.at said station set,a' magneti'dholdiiig relay, 2. second set of contacts connected to saidline and jointly controlled mechanically at said station set andmagnetically by said holding relay, means responsive to the initiationof a call to actuate said first set of contacts for connecting saidmagnetic holding relay to said line, and other apparatus responsive to apredetermined electrical signal for actuating said holding relay toactuate said second pair of contacts for disconnecting said holdingrelay from said line.

11. In a telephone switching system, a subscribers line, a subscriber'sstation connected thereto comprising telephone transmitting andreceiving equipment, call signal generating equipment, a magneticholding relay, a first set of contacts mechanically controlled at saidstation, a second set of contacts jointly controlled at said station andby said magnetic holding relay, means responsive to the actuation ofsaid first set of contacts at said station to initiate a call and toconnect said magnetic holding relay and said call signal generatingequipment to said line, and other means responsive to a predetermined'electrical signal condition applied to said line for actuating saidholding relay to operate said second set of contacts to disconnect saidmagnetic holding relay and said call signal generating apparatus fromsaid line.

12. In a telephone switching system, a subscribers line, a subscribersstation connected thereto comprising telephone transmitting and callsignal generating equipment, a magnetic holding'relay, a first set ofcontacts mechanically controlled at said station, a second set ofcontacts jointly controlled at said station and by said magnetic holdingrelay, means responsive to the actuation of said first set of contactsat said station to initiate a call and to connect said magnetic holdingrelay and said call signal generating equipment to said line, and othermeans responsive to a predetermined electrical signal condition appliedto said line for actuating said holding relay to actuate said second setof contacts to disconnect said magnetic holding relay and said callsignal generating apparatus from said line, and for connecting saidtelephone transmitting and receiving equipment to said line.

13. In a telephone switching system, a subscribers line, a subscriber'sstation connected thereto comprising telephone transmitting andreceiving equipment, call signal generating equipment, a magneticholding relay, a first set of contacts mechanically controlled at saidstation, a second set of contacts jointly controlled at said stationand, by said magnetic holding relay, means responsive to the actuationof said first set of contacts at said station to initiate a call and toconnect said magnetic holding relay and said call signal generatingequipment to said line, other means responsive to a predeterminedelectrical signal condition applied to said line for actuating saidholding relay to move said second set of contacts to disconnect saidmagnetic holding relay and said call signal generating apparatus fromsaid line, and for connecting said telephone transmitting and receivingequipment to said line, and apparatus responsive to actuation of bothsets of contacts by said subscriber for transmitting a recalled signalover said line.

14. In a telephone switching system, a subscribers line, a subscriber'sstation set connected thereto, signaling apparatus for signaling oversaid line included in said subscriber's station set,

communication apparatus also included in said subscriber's station, set,.a magnetic holding device, a first set of contacts mechanicallycontrolled at said station set, a second set of con tacts mechanicallycontrolled at said stationset and over said line bysaid magneticholdingdevice, means responsive to the actuation'of said first set of contactsfor initiating a call and connecting said magnetic holding device andsaid signaling apparatus to said line, apparatus responsive to theactuation of, saidsecond set of contacts for disconnecting said magneticholding device and said signaling apparatus from said line andconnecting said communication apparatus to said line,apparatusresponsive to the answering of a call for substantiallysimultaneously operating both sets 01' said contacts, and meansoperative after the connection of said communication equipment to saidline for transmitting a flashing or recall signal over said line by thesimultaneous actuation in both directions of both sets of said contacts.

KERMIT s. DUNLAP.

i 4 i 1 i

